It has been known that semiconductor devices have a superlattice structure in which there is periodic variation in semiconductor composition, this having been shown and described, for example in U.S. Pat. Nos. 3,626,257 and 3,626,328, which were issued to Leo Esaki et al. on Dec. 7, 1971. The layered structure disclosed therein comprises a one-dimensional transport device that is formed either by doping or by alloying techniques.
In U.S. Pat. No. 4,103,312, issued to L. L. Chang et al. on June 25, 1978, there is disclosed a multilayered sandwich-type heterostructure comprising alternating layers of different semiconductor materials forming a periodic structure, and which is adapted to provide a three-dimensional confinement of electrons and holes in the device. A multilayered semiconductor heterostructure wherein potential wells are created between layers is disclosed in U.S. Pat. No. 4,257,055 issued to K. Hess et al. on Mar. 17, 1981. There, an inner layer exhibits high charge-carrier mobility and a relatively narrow band-gap characteristic, while the outer sandwich layers exhibit low charge mobilities and larger band gap characteristics and are operable such that, under quiescent conditions, the charge carriers of the outer sandwich layers reside in the inner layer that is due to the potential well that is created by the band-gap difference between the layers.
In U.S. Pat. No. 4,503,447, issued to G. J. Iafrate, T. R. AuCoin and D. K. Ferry on Mar. 5, 1985, a two-dimensional lateral superlattice structure within a single layer of semiconductor material was disclosed. The semiconductor device structure, including a plurality of multidimensional charge carrier confinement regions of a cylindrically formed semiconductor material exhibiting a relatively high charge-carrier mobility and a surrounding low band-gap semiconductor, that is laterally located in a single planar layer exhibiting a relatively low charge-carrier mobility and high band-gap, yields periodic regions that are adapted to act as quantum-well confinement regions for electrons. It is disclosed that the structures are formed, for example, by appropriate high-resolution lithography, physically etching the semiconductor to minimum feature sizes of the order of the deBroglie wavelength for a charge-carrier, for example, 250 .ANG. in gallium arsenide, and followed by selective area epitaxial overgrowth.